Controlling multiple modems in a wireless terminal using energy-per-bit determinations

ABSTRACT

A mobile wireless terminal (MWT) includes multiple wireless modems. The multiple modems have their respective transmit outputs combined to produce an aggregate transmit output. The multiple modems can concurrently transmit data in a reverse link direction and receive data in a forward link direction. The MWT is constrained to operate under an aggregate transmit power limit. Each of the multiple modems has an individual transmit limit related to the aggregate transmit power limit. An MWT controller controls the total number of modems that transmit data at any given time, based on an average energy-per-transmitted bit, or alternatively, individual energy-per-transmitted bits of the modems.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present Application for Patent is a Continuation and claims priorityto patent application Ser. No. 10/283,935 entitled “CONTROLLING MULTIPLEMODEMS IN A WIRELESS TERMINAL USING ENERGY-PER-BIT DETERMINATIONS”filedOct. 29, 2002, now allowed, and assigned to the assignee hereof andhereby expressly incorporated by reference herein.

REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT

This application is related to commonly-owned applications, entitled“Wireless Terminal Operating Under An Aggregate Transmit Power LimitUsing Multiple Modems Having Fixed Individual Transmit Power Limits”having U.S. patent application Ser. No. 10/283,676, filed on Oct. 29,2002, and “Controlling Multiple Modems In A Wireless Terminal UsingDynamically Varying Modem Transmit Power Limits” having U.S. patentapplication Ser. No. 10/283,934, filed Oct. 29, 2002, which areincorporated herein by reference.

BACKGROUND

1. Field

The present invention relates generally to mobile wireless terminals,and particularly, to mobile wireless terminals having multiple modemswhich are constrained to operate under an aggregate transmit power limitfor all of the modems.

2. Background

In a data call established between a mobile wireless terminal (MWT) anda remote station, the MWT can transmit data to the remote station over a“reverse” communication link. Also, the MWT can receive data from theremote station over a “forward” communication link. There is an everpressing need to increase the transmit and receive bandwidth, that is,the data rates, available over both the forward and reverse links.

Typically, the MWT includes a transmit power amplifier to power-amplifya radio frequency (RF) input signal. The power amplifier produces anamplified, RF output signal having an output power responsive to theinput power of the input signal. An inordinately high input power mayover-drive the power amplifier, and thus cause the output power toexceed an acceptable operating transmit power limit of the poweramplifier. In turn, this may cause undesired distortion of the RF outputsignal, including unacceptable out-of-band RF emissions.

Therefore, there is a need to carefully control the input and/or outputpower of the transmit power amplifier in an MWT so as to avoidover-driving the power amplifier. There is a related need to control theoutput power as just mentioned, while minimizing to the extent possible,any reduction of the forward and reverse link bandwidth (that is, datarates).

SUMMARY

A feature of the present invention is to provide an MWT that maximizesan overall communication bandwidth in both the reverse and forward linkdirections using a plurality of concurrently operating communicationlinks, each associated with a respective one of a plurality ofmodulator-demodulators (modems) of the MWT.

Another feature of the present invention is to provide an MWT thatcombines multiple modulator-demodulator (modem) transmit signals into anaggregate transmit signal (that is, an aggregate reverse link signal) sothat a single transmit power amplifier can be used. This advantageouslyreduces power consumption, cost, and space requirements compared toknown systems using multiple power amplifiers.

Another feature of the present invention is to carefully control anaggregate input and/or output power of the transmit power amplifier,thereby avoiding signal distortion at the power amplifier output. Arelated feature is to control the aggregate input and/or output power insuch a manner as to maximize bandwidth (that is, data through-put) inboth the reverse and forward link directions.

These features are achieved in several ways. First, individual transmitpower limits are established in each of the plurality of modems of thewireless terminal, to limit the respective, individual modem transmitpowers. Each individual transmit power limit is derived, in part, froman aggregate transmit power limit for all of the modems. Together, theindividual transmit power limits collectively limit the aggregatetransmit power of all of the modems.

Second, the present invention controls the total number of modemspermitted to transmit data at any given time, so as to maximize anaggregate transmit data rate of the wireless terminal while maintainingthe aggregate transmit power of all of the modems below the aggregatetransmit power limit. To do this, the present invention collects and/ordetermines modem transmit statistics corresponding to a previoustransmit period or cycle of the wireless terminal. The modem transmitstatistics can include individual modem transmit data rates, individualmodem transmit powers, the aggregate transmit data rate of all of themodems, and an aggregate transmit power for all of the modems combined.

The statistics are used to determine an average energy-per-transmittedbit across all of the modems, or alternatively, individualenergy-per-transmitted bits for each of the modems, corresponding to theprevious transmit cycle of the wireless terminal. Then, either theaverage or individual energy-per-transmitted-bits are used to determinea maximum number of “active” modems that can be scheduled to transmitdata concurrently, and preferably at their respective maximum datarates, without exceeding the aggregate transmit power limit of thewireless terminal. This maximum number of active modems are scheduled totransmit data during the next transmit cycle of the wireless terminal.The invention repeats the process periodically, to update the maximumnumber of active modems over time. In this manner, the present inventionattempts, proactively, to avoid “over-limit” conditions in the modems ofthe wireless terminal. An over-limit modem has an actual transmit power,or alternatively, a required transmit power, that exceeds the individualtransmit power limit established in the modem.

In the present invention, only active modems are scheduled to transmitdata in the reverse link direction. “Inactive” modems are modems thatare not scheduled to transmit data. However, in the present invention,inactive modems are able to receive data in the forward link direction,thereby maintaining a high forward link through-put in the wirelessterminal, even when modems are inactive in the reverse link direction.

The present invention is directed to an wireless terminal including aplurality (N) of wireless modems. The N modems have their respectivetransmit outputs combined to produce an aggregate transmit output. The Nmodems can concurrently transmit data in the reverse link direction andreceive data in the forward link direction. The wireless terminal isconstrained to operate within an aggregate transmit power limit. Oneaspect of the present invention is a method, comprising: scheduling aplurality, M, of active ones (that is active individual members) of theN modems to transmit payload data, where M is less than or equal to N;monitoring status reports from at least the active modems; determining,based on the status reports, whether to adjust/modify the number ofactive modems in order to maximize an aggregate transmit data rate ofthe N modems while maintaining an aggregate transmit power of the Nmodems at or below the aggregate transmit power limit; and modifying thenumber of active modems when it is determined that the number of activemodems should be modified to maintain the aggregate transmit power levelof the N modems at or below the aggregate transmit power level. This andfurther aspects of the present invention are described below.

The step of determining can comprise determining a maximum number ofactive modems that can concurrently transmit data, each at apredetermined maximum data rate, while maintaining the aggregatetransmit power of the N modems at or below the aggregate transmit powerlimit, and comparing the maximum number of active modems to the number Mof active modems. The maximum number can be determined by determining anaverage energy-per-transmitted-bit across at least the M active modemsand the aggregate transmit power limit. Here, the status reports beingmonitored indicate a respective transmit data rate for each of the Nmodems while determining the average energy-per-transmitted-bit cancomprise determining an aggregate transmit data rate across the N modemsbased on their respective transmit data rates and determining theaggregate transmit power. The status reports monitored can indicate arespective transmit power for each of the N modems.

In further aspects of the method, next active modems can be selected asthe maximum number of modems having the lowest individualenergy-per-transmitted-bits among the N modems, and the schedulingprocess is repeated using these next active modems. The number of activemodems can be increased to the maximum number when the maximum number isgreater than M, and decreased to the maximum number when the maximumnumber is less than M.

The method can include activating a selected, previously inactive one ofthe N modems, thereby increasing the number of active modems, andincreasing the respective transmit power limit in the selected one ofthe N modems. Alternatively, a selected, previously active one of the Nmodems, is deselected thereby decreasing the number of active modems;and the respective transmit power limit in the selected one of the Nmodems is decreased. Each of the N modems is adapted to transmit data atat least one of a maximum transmit data rate and a minimum transmit datarate; and the maximum number of active modems is based on the minimumand maximum transmit data rates as well as the averageenergy-per-transmitted-bit and the aggregate transmit power limit.

The N modems can be sorted according to their respective individualenergy-per-transmitted-bits and scheduling includes using the maximumnumber of active modems having the lowest individualenergy-per-transmitted-bits among the N modems.

The invention also includes a method of dynamically calibrating a dataterminal including N wireless modems having their respective transmitoutputs combined to produce an aggregate transmit output, the methodcomprising scheduling each of the N modems to concurrently transmitrespective data; receiving respective reported transmit powersP_(Rep)(i) from the N modems corresponding to when the N modemsconcurrently transmit, where i designates a respective modem from 1 toN; measuring an aggregate transmit power P_(Agg) corresponding to whenthe N modems concurrently transmit; generating an equation representingthe aggregate transmit power as a cumulative function of each reportedtransmit power P_(Rep)(i) and a corresponding, undetermined, modemdependent gain factor g(i); repeating these steps N times to generate Nsimultaneous equations; and determining all of the modem dependent gainfactors from the N simultaneous equations. Furthermore these steps canbe periodically repeated so that the modem dependent gain factors areupdated periodically.

In further aspects of the invention, a wireless terminal is providedwhich is constrained to operate under an aggregate transmit power limit,having N wireless modems with their respective transmit outputs combinedtogether to produce an aggregate transmit output. The terminal comprisesmeans for scheduling a plurality, M, of active ones of the N modems totransmit payload data, where M is less than or equal to N; means formonitoring status reports from at least the active modems; means fordetermining, based on the status reports, whether to modify the numberof active modems in order to maximize an aggregate transmit data rate ofthe N modems while maintaining an aggregate transmit power of the Nmodems at or below the aggregate transmit power limit; and means formodifying the number of active modems when it is determined the numbershould be modified to maintain the aggregate transmit power level at orbelow the aggregate transmit power level.

The determining means in the wireless terminal may comprise means fordetermining a maximum number of active modems that can concurrentlytransmit data, each at a predetermined maximum data rate, whilemaintaining the aggregate transmit power of the N modems at or below theaggregate transmit power limit, and means for comparing the maximumnumber of active modems to the number M of active modems.

In further embodiments, the means for determining the maximum numbercomprises means for determining an average energy-per-transmitted-bitacross at least the M active modems or an individualenergy-per-transmitted-bit for each of the N modems, and means fordetermining the maximum number of active modems based on the average orindividual energy-per-transmitted-bits, respectively, and the aggregatetransmit power limit. The monitored status reports indicate a respectivetransmit data rate or transmit power for each of the N modems. The meansfor determining the average energy-per-transmitted-bit comprises meansfor determining an aggregate transmit data rate across the N modemsbased on their respective transmit data rates, means for determining theaggregate transmit power, and means for determining the averageenergy-per-transmitted-bit based on the aggregate transmit data rate andthe aggregate transmit power.

The wireless terminal may include means for selecting as next activemodems the maximum number of modems having the lowest individualenergy-per-transmitted-bits among the N modems. The modifying means cancomprise means for increasing the number of active modems to the maximumnumber when the maximum number is greater than M, or means fordecreasing the number of active modems to the maximum number when themaximum number is less than M. The modifying means can include means foractivating a selected, previously inactive one of the N modems, therebyincreasing the number of active modems, and means for increasing therespective transmit power limit in the selected one of the N modems. Themodifying means can comprise means for deactivating a selected,previously active one of the N modems, thereby decreasing the number ofactive modems; and decreasing the respective transmit power limit in theselected one of the N modems.

In further aspects, each of the N modems is adapted to transmit data atat least one of a maximum transmit data rate and a minimum transmit datarate, and the means for determining the maximum number comprisesdetermining the maximum number based on the minimum and maximum transmitdata rates as well as the average energy-per-transmitted-bit and theaggregate transmit power limit.

A wireless terminal constrained to operate within an aggregate transmitpower limit, having N wireless modems with their respective transmitoutputs combined to produce an aggregate transmit output, comprisingmeans for determining an individual energy-per-transmitted-bit for eachof the N modems that was previously transmitting, means for determining,based on individual energy-per-transmitted-bits and the aggregatetransmit power limit, a maximum number of active modems that canconcurrently transmit data at a maximum data rate without exceeding theaggregate transmit power limit, and means for scheduling the maximumnumber of active modems to transmit data.

In further aspects the wireless terminal further comprises means forsorting the N modems according to their respective individualenergy-per-transmitted-bits, while the means for scheduling comprisesmeans for scheduling the maximum number of active modems having thelowest individual energy-per-transmitted-bits among the N modems. Thewireless terminal further comprises means for monitoring status reportsfrom at least the active modems, which collectively include a transmitpower estimate of each active modem, wherein the means for determiningthe individual energy-per-transmitted-bits comprises means fordetermining, from each transmit power estimate, the correspondingindividual energy-per-transmitted-bit.

Apparatus for dynamically calibrating a wireless terminal including Nwireless modems having their respective transmit outputs combined toproduce an aggregate transmit output. The apparatus comprises means forscheduling each of the N modems to concurrently transmit respectivedata, means for receiving respective reported transmit powers P_(Rep)(i)from the N modems, a power meter, coupled to the aggregate transmitoutput, for measuring an aggregate transmit power P_(Agg) of the Nmodems, means for generating a representation of the aggregate transmitpower as a cumulative function of each reported transmit powerP_(Rep)(i) and a corresponding, undetermined, modem dependent gainfactor g(i), wherein the scheduling means, the receiving means, thepower meter, and the generating means repeat their respective functionsN times to generate N simultaneous equations, and means for determiningall of the modem dependent gain factors from the N simultaneousequations.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objects, and advantages of the present invention willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify the same or similar elements throughout and wherein:

FIG. 1 is an illustration of an example wireless communication system.

FIG. 2 is a block diagram of an example mobile wireless terminal.

FIG. 3 is a block diagram of an example modem representative ofindividual modems of the mobile wireless terminal of FIG. 2.

FIG. 4 is an illustration of an example data frame that may betransmitted or received by any one of the modems of FIGS. 2 and 3.

FIG. 5 is an illustration of an example status report from the modems ofFIGS. 2 and 3.

FIG. 6 is a flowchart of an example method performed by each of themodems of FIGS. 2 and 3.

FIG. 7 is a flowchart of an example method performed by the mobilewireless terminal.

FIG. 8 is a flowchart expanding on the method of FIG. 7.

FIG. 9 is a flowchart expanding on the method of FIG. 7.

FIG. 10 is a flowchart of another example method performed by the mobilewireless terminal.

FIG. 11 is an example plot of Power versus Modem index(i) identifyingrespective ones of the modems of FIG. 2, wherein uniform modem transmitpower limits are depicted. FIG. 11 also represents an example transmitscenario of the mobile wireless terminal of FIG. 2.

FIG. 12 is another example transmit scenario similar to FIG. 11.

FIG. 13 is an illustration of an alternative, tapered arrangement forthe modem transmit power limits.

FIG. 14 is a flowchart of an example method of calibrating modems in themobile wireless terminal of FIG. 2.

FIG. 15 is a flowchart of an example method of operating the mobilewireless terminal, using dynamically updated individual modem transmitpower limits.

FIG. 16 is a flowchart of an example method expanding on the method ofFIG. 15.

FIG. 17 is a flowchart of an example method of determining a maximumnumber of active modems using an average energy-per-transmitted-bit ofthe modems.

FIG. 18 is a flowchart of an example method of determining a maximumnumber of active modems, using an individual energy-per-transmitted-bitfor each of the modems.

FIG. 19 is a graphical representation of different modem transmit limitarrangements.

FIG. 20 is a functional block diagram of an example controller of themobile wireless terminal of FIG. 2, for performing the methods of thepresent invention.

DETAILED DESCRIPTION

A variety of multiple access communication systems and techniques havebeen developed for transferring information among a large number ofsystem users. However, spread spectrum modulation techniques, such asthose used in code division multiple access (CDMA) communication systemsprovide significant advantages over other modulation schemes, especiallywhen providing service for a large number of communication system users.Such techniques are disclosed in the teachings of U.S. Pat. No.4,901,307, which issued Feb. 13, 1990 under the title “Spread SpectrumMultiple Access Communication System Using Satellite or TerrestrialRepeaters” to Gilhousen et al., and U.S. Pat. No. 5,691,974, whichissued Nov. 25, 1997, entitled “Method and Apparatus for Using FullSpectrum Transmitted Power in a Spread Spectrum Communication System forTracking Individual Recipient Phase Time and Energy” to Carter et al.,both of which are assigned to the assignee of the present invention, andare incorporated herein by reference in their entirety.

The method for providing CDMA mobile communications was standardized inthe United States by the Telecommunications Industry Association inTIA/EIA/IS-95-A entitled “Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System,”referred to herein as IS-95. Other communications systems are describedin other standards such as the IMT-2000/UM, or International MobileTelecommunications System 2000/Universal Mobile TelecommunicationsSystem, standards covering what are referred to as wideband CDMA(WCDMA), cdma2000 (such as cdma2000 1× or 3× standards, for example) orTD-SCDMA.

I. Example Communication Environment

FIG. 1 is an illustration of an exemplary wireless communication system(WCS) 100 that includes a base station 112, two satellites 116 a and 116b, and two associated gateways (also referred to herein as hubs) 120 aand 120 b. These elements engage in wireless communications with userterminals 124 a, 124 b, and 124 c. Typically, base stations andsatellites/gateways are components of distinct terrestrial and satellitebased communication systems. However, these distinct systems mayinter-operate as an overall communications infrastructure.

Although FIG. 1 illustrates a single base station 112, two satellites116, and two gateways 120, any number of these elements may be employedto achieve a desired communications capacity and geographic scope. Forexample, an exemplary implementation of WCS 100 includes 48 or moresatellites, traveling in eight different orbital planes in Low EarthOrbit (LEO) to service a large number of user terminals 124.

The terms base station and gateway are also sometimes usedinterchangeably, each being a fixed central communication station, withgateways, such as gateways 120, being perceived in the art as highlyspecialized base stations that direct communications through satelliterepeaters while base stations (also sometimes referred to ascell-sites), such as base station 112, use terrestrial antennas todirect communications within surrounding geographical regions.

In this example, user terminals 124 each have or include apparatus or awireless communication device such as, but not limited to, a cellulartelephone, wireless handset, a data transceiver, or a paging or positiondetermination receiver. Furthermore each of user terminals 124 can behand-held, portable as in vehicle-mounted (including for example cars,trucks, boats, trains, and planes), or fixed, as desired. For example,FIG. 1 illustrates user terminal 124 a as a fixed telephone or datatransceiver, user terminal 124 b as a hand-held device, and userterminal 124 c as a portable vehicle-mounted device. Wirelesscommunication devices are also sometimes referred to as mobile wirelessterminals, user terminals, mobile wireless communication devices,subscriber units, mobile units, mobile stations, mobile radios, orsimply “users,” “mobiles,” “terminals,” or “subscribers” in somecommunication systems, depending on preference.

User terminals 124 engage in wireless communications with other elementsin WCS 100 through CDMA communications systems. However, the presentinvention may be employed in systems that employ other communicationstechniques, such as time division multiple access (TDMA), and frequencydivision multiple access (FDMA), or other waveforms or techniques listedabove (WCDMA, CDMA2000 . . . ).

Generally, beams from a beam source, such as base station 112 orsatellites 116, cover different geographical areas in predefinedpatterns. Beams at different frequencies, also referred to as CDMAchannels, frequency division multiplexed (FDM) channels, or “sub-beams,”can be directed to overlap the same region. It is also readilyunderstood by those skilled in the art that beam coverage or serviceareas for multiple satellites, or antenna patterns for multiple basestations, might be designed to overlap completely or partially in agiven region depending on the communication system design and the typeof service being offered, and whether space diversity is being achieved.

FIG. 1 illustrates several exemplary signal paths. For example,communication links 130 a-c provide for the exchange of signals betweenbase station 112 and user terminals 124. Similarly, communications links138 a-d provide for the exchange of signals between satellites 116 anduser terminals 124. Communications between satellites 116 and gateways120 are facilitated by communications links 146 a-d.

User terminals 124 are capable of engaging in bi-directionalcommunications with base station 112 and/or satellites 116. As such,communications links 130 and 138 each include a forward link and areverse link. A forward link conveys information signals to userterminals 124. For terrestrial-based communications in WCS 100, aforward link conveys information signals from base station 112 to a userterminal 124 across a link 130. A satellite-based forward link in thecontext of WCS 100 conveys information from a gateway 120 to a satellite116 over a link 146 and from the satellite 116 to a user terminal 124over a link 138. Thus, terrestrial-based forward links typically involvea single wireless signal path between the user terminal and basestation, while satellite-based links typically involve two, or more,wireless signal paths between the user terminal and a gateway through atleast one satellite (ignoring multipath).

In the context of WCS 100, a reverse link conveys information signalsfrom a user terminal 124 to either a base station 112 or a gateway 120.Similar to forward links in WCS 100, reverse links typically require asingle wireless signal path for terrestrial-based communications and twowireless signal paths for satellite-based communications. WCS 100 mayfeature different communications offerings across these forward links,such as low data rate (LDR) and high data rate (HDR) services. Anexemplary LDR service provides forward links having data rates from 3kilobits per second (kbps) to 9.6 kbps, while an exemplary HDR servicesupports typical data rates as high as 604 kbps and higher.

As described above, WCS 100 performs wireless communications accordingto CDMA techniques. Thus, signals transmitted across the forward andreverse links of links 130, 138, and 146 convey signals that areencoded, spread, and channelized according to CDMA transmissionstandards. In addition, block interleaving can be employed for theseforward and reverse links. These blocks are transmitted in frames havinga predetermined duration, such as 20 milliseconds.

Base station 112, satellites 116, and gateways 120 may adjust the powerof the signals that they transmit over the forward links of WCS 100.This power (referred to herein as forward link transmit power) may bevaried according to user terminal 124 and according to time. This timevarying feature may be employed on a frame-by-frame basis. Such poweradjustments are performed to maintain forward link bit error rates (BER)within specific requirements, reduce interference, and conservetransmission power.

User terminals 124 may adjust the power of the signals that theytransmit over the reverse links of WCS 100, under the control ofgateways 120 or base stations 112. This power (referred to herein asreverse link transmit power) may be varied according to user terminal124 and according to time. This time varying feature may be employed ona frame-by-frame basis. Such power adjustments are performed to maintainreverse link bit error rates (BER) within specific requirements, reduceinterference, and conserve transmission power.

Examples of techniques for exercising power control in CDMAcommunication systems are found in U.S. Pat. No. 5,383,219 issued Jan.17, 1995, entitled “Fast Forward Link Power Control In A Code DivisionMultiple Access System” to Padovani et al., U.S. Pat. No. 5,396,516issued Mar. 7, 1995, entitled “Method And System For The DynamicModification Of Control Parameters In A Transmitter Power ControlSystem” to Padovani et al., and U.S. Pat. No. 5,056,109 issued Oct. 8,1991, entitled “Method and Apparatus For Controlling Transmission PowerIn A CDMA Cellular Mobile Telephone System” to Gilhousen et al., whichare incorporated herein by reference.

II. Mobile Wireless Terminal

FIG. 2 is a block diagram of an example MWT 206 constructed and operatedin accordance with the principles of the present invention. MWT 206communicates wirelessly with a base station or gateway (referred to as aremote station), not shown in FIG. 2. Also, MWT 206 may communicate witha user terminal. MWT 206 receives data from external data sources/sinks,such as a data network, data terminals, and the like, over acommunication link 210, such as an Ethernet link, for example. Also, MWT206 sends data to the external data sources/sinks over communicationlink 210.

MWT 206 includes an antenna 208 for transmitting signals to andreceiving signals from the remote station. MWT 206 includes a controller(that is, one or more controllers) 214 coupled to communication link210. Controller 214 exchanges data with a memory/storage unit 215, andinterfaces with a timer 217. Controller 214 providesdata-to-be-transmitted to, and receives data from, a plurality ofwireless modems 216 a-216 n over a plurality of correspondingbi-directional data links 218 a-218 n between controller 214 and modems216. Data links 218 may be serial data connections. The number N ofmodems that may be used can be one of several values, as desired,depending on known design issues such as complexity, cost, and so forth.In an example implementation, N=16.

Wireless modems 216 a-216 n provide RF signals 222 a _(T)-222 n _(T) toand receive RF signals 222 a _(R)-222 n _(R) from a powercombiner/splitter assembly 220, over a plurality of bi-directional RFconnections/cables between the modems and the power combiner/splitterassembly 220 (hereinafter “assembly 220”). In a transmit (that is,reverse link) direction, a power combiner included in assembly 220combines together the RF signals received from all of modems 216, andprovides a combined (that is, aggregate) RF transmit signal 226 to atransmit power amplifier 228. Transmit power amplifier 228 provides anamplified, aggregate RF transmit signal 230 to a duplexer 232.

Duplexer 232 provides the amplified, aggregate RF transmit signal toantenna 208. In MWT 206, duplexing may be achieved by means other thanduplexer 232, such as using separate transmit and receive antennas.Also, a power monitor 234, coupled to an output of power amplifier 228,monitors a power level of amplified, aggregate transmit signal 230.Power monitor 234 provides a signal 236 indicating the power level ofamplified, aggregate transmit signal 230 to controller 214. In analternative arrangement of MWT 206, power monitor 234 measures the powerlevel of aggregate signal 226 at the input to transmit amplifier 228. Inthis alternative arrangement, the aggregate transmit power limit of MWT206 is specified at the input to transmit amplifier 228 instead of atits output, and the methods of the present invention, described below,take this into account.

In a receive (that is, forward link) direction, antenna 208 provides areceived signal to duplexer 232. Duplexer 232 routes the received signalto a receive amplifier 240. Receive amplifier 240 provides an amplifiedreceived signal to assembly 220. A power splitter included in assembly220 divides the amplified received signal into a plurality of separatereceived signals and provides each separate signal to a respective oneof the modems 216.

MWT 206 communicates with the remote station over a plurality ofwireless CDMA communication links 250 a-250 n established between MWT206 and the remote station. Each of the communication links 250 isassociated with a respective one of modems 216. Wireless communicationlinks 250 a-250 n can operate concurrently with one another. Each ofwireless communication links 250 supports wireless traffic channels forcarrying data between MWT 206 and the remote station in both forward andreverse link directions. The plurality of wireless communicationchannels 250 form part of an air interface 252 between MWT 206 and theremote station.

In the present embodiment, MWT 206 is constrained to operate under anaggregate transmit power limit (APL) at the output of transmit amplifier228. In other words, MWT 206 is required to limit the transmit power ofsignal 230 to a level that is preferably below the aggregate transmitpower limit. All of modems 216, when transmitting, contribute to theaggregate transmit power of signal 230. Accordingly, the presentinvention includes techniques to control the transmit powers of modems216, and thereby cause the aggregate transmit power of modems 216, asmanifested in transmit signal 230, to be under the aggregate transmitpower limit.

Over-driving transmit amplifier 228 causes the power level of signal 230to exceed the aggregate transmit power limit. Therefore, the presentinvention establishes individual transmit power limits (also referred toas transmit limits) for each of modems 216. The individual transmitpower limits are related to the aggregate transmit power limit in such away as to prevent modems 216 from collectively over-driving transmitamplifier 228. During operation of MWT 206, the present inventioncontrols a maximum number of active modems that can concurrentlytransmit data at any given time so as to maximize the aggregate transmitdata rate of the MWT, while maintaining the aggregate transmit power ofall of modems 216 at or below the aggregate transmit power limit. Thepresent invention uses proactive techniques to avoid over-limitconditions in modems 216. Further aspects of the present invention aredescribed below.

Although MWT 206 is referred to as being mobile, it is to be understoodthat the MWT is not limited to a mobile platform, or portable platforms.For example, MWT 206 may reside in a fixed base station or gateway. MWT206 may also reside in a fixed user terminal 124 a.

III. Modem

FIG. 3 is a block diagram of an example modem 300 representative of eachof modems 216. Modem 300 operates in accordance with CDMA principles.Modem 300 includes a data interface 302, a controller 304, a memory 306,a modem signal processor or module 308, such as one or more digitalsignal processors (DSP) or ASICs, an intermediate frequency IF/RFsubsystem 310, and an optional power monitor 312, all coupled to oneanother over a data bus 314. In some systems, the modems do not comprisetransmit and receive processors coupled in pairs as in a moretraditional modem structure, but may use an array of transmitters andreceivers or modulators and demodulators which are interconnected, asdesired, to handle user communications, and one or more signals, orotherwise time shared among users.

In the transmit direction, controller 304 receivesdata-to-be-transmitted from controller 214 over data connection 218 i(where “i” indicates any one of the modems 216 a-216 n), and throughinterface 302. Controller 304 provides the data-to-be-transmitted tomodem processor 308. A transmit (Tx) processor 312 of modem processor308 encodes and modulates the data-to-be-transmitted, and packages thedata into data frames that are to be transmitted. Transmit processor 312provides a signal 314 including the data frames to IF/RF subsystem 310.Subsystem 310 frequency up-converts and amplifies signal 314, andprovides a resulting frequency up-converted, amplified signal 222 i _(T)to power combiner/splitter assembly 220. Optional power meter 320monitors a power level of signal 222 i _(T) (that is, the actualtransmit power at which modem 300 transmits the above-mentioned dataframes). Alternatively, modem 300 can determine the modem transmit powerbased on gain/attenuator settings of IF/RF subsystem 310 and the datarate at which modem 300 transmits the data frames.

In the receive direction, IF/RF subsystem 310 receives a received signal222 i _(R) from power combiner/splitter assembly 220, frequencydown-converts signal 222 i _(R) and provides the resulting frequencydown-converted signal 316, including received data frames, to a receive(Rx) processor 318 of modem processor 308. Receive processor 318extracts data from the data frames, and then controller 304 provides theextracted data to controller 214, using interface 302 and dataconnection 218 i.

Modems 216 each transmit and receive data frames in the manner describedabove and further below. FIG. 4 is an illustration of an example dataframe 400 that may be transmitted or received by any one of modems 216.Data frame 400 includes a control or overhead field 402 and a payloadfield 404. Fields 402 and 404 include data bits used to transfer eithercontrol information (402) or payload data (404). Control field 402includes control and header information used in managing a communicationlink established between a respective one of modems 216 and the remotestation. Payload field 404 includes payload data (bits 406), forexample, data-to-be-transmitted between controller 214 and the remotestation during a data call (that is, over the communication linkestablished between the modem and the remote station). For example, datareceived from controller 214, over data link 218 i, is packaged intopayload field 404.

Data frame 400 has a duration T, such as 20 milliseconds, for example.The payload data in payload field 404 is conveyed at one of a pluralityof data rates, including a maximum or full-rate (for example, 9600bits-per-second (bps)), a half-rate (for example, 4800 bps), aquarter-rate (for example, 2400 bps), or an eighth-rate (for example,1200 bps). Each of the modems 216 attempts to transmit data at thefull-rate (that is, at a maximum data rate). However, an over-limitmodem rate-limits, whereby the modem reduces its transmit data rate fromthe maximum rate to a lower rate, as will be discussed below. Also, eachof the modems 216 may transmit a data frame (for example, data frame400) without payload data. This is referred to as a zero-rate dataframe.

In one modem arrangement, each of the data bits 406 within a framecarries a constant amount of energy, regardless of the transmit datarate. That is, within a frame, the energy-per-bit, E_(b), is constantfor all of the different data rates. In this modem arrangement, eachdata frame corresponds to an instantaneous modem transmit power that isproportional to the data rate at which the data frame is transmitted.Therefore, the lower the data rate, the lower the modem transmit power.

Each of the modems 216 provides status reports to controller 214 overrespective data connections 218. FIG. 5 is an illustration of an examplestatus report 500. Status report 500 includes a modem data rate field502, a modem transmit power field 504, and an optional over-limit (alsoreferred to as a rate-limiting) indicator field 506. Each modem reportsthe data rate of the last transmitted data frame in field 502, and thetransmit power of the last transmitted data frame in field 504. Inaddition, each modem can optionally report whether it is in arate-limiting condition in field 506.

In another alternative modem arrangement, the modem can provide statussignals indicating the over-limit/rate-limiting condition, the transmitpower, and transmit data rate of the modem.

IV. Example Method

FIG. 6 is a flowchart of an example method or process 600 representativeof an operation of modem 300, and thus, of each of modems 216. Method600 assumes a data call has been established between a modem (forexample, modem 216 a) and the remote station. That is, a communicationlink including a forward link and a reverse link has been establishedbetween the modem and the remote station.

At a first step 602, a transmit power limit P_(L) is established in themodem (for example, in modem 216 a).

At a next step 604, the modem receives a power control command from theremote station over the forward link indicating a requested transmitpower P_(R) at which the modem is to transmit data frames in the reverselink direction. This command may be in the form of an incremental powerincrease or decrease command.

At a decision step 606, the modem determines whether any payload datahas been received from controller 214, that is, whether or not there isany payload data to transmit to the remote station. If not, processingof the method proceeds to a next step 608. At step 608, the modemtransmits a data frame at the zero-rate, that is, without payload data.The zero-rate data frame may include control/overhead information usedto maintain the communication link/data call, for example. The zero-ratedata frame corresponds to a minimum transmit power of the modem.

On the other hand, if there is payload data to transmit, then processing(control) proceeds from step 606 to a next step 610. At step 610, themodem determines whether or not it is not over-limit, that is, whetherthe modem is under-limit. In one arrangement, determining whether themodem is under-limit includes determining whether the requested transmitpower P_(R) is less than the transmit power limit P_(L). In thisarrangement, the modem is considered over-limit when the requestedtransmit power P_(R) is greater than or equal to P_(L). In analternative arrangement, determining whether or not the modem isunder-limit includes determining whether an actual transmit power P_(T)of the modem is less than the transmit power limit P_(L). In thisarrangement, the modem is considered over-limit when P_(T) is greaterthan or equal P_(L). The modem may use power meter 320 in determiningwhether its transmit power P_(T), for example, the transmit power ofsignal 222 i _(T), is less than the transmit power limit P_(L).

While the modem is not-over limit, the modem transmits a data frame,including payload data and control information, at a maximum data rate(for example, the full-rate) and at a transmit power level P_(T) that isin accordance with the requested transmit power P_(R). In other words,the modem transmit power P_(T) tracks the requested transmit powerP_(R).

When P_(T) or P_(R) is equal to or greater than P_(L), the modem isover-limit, and thus rate-limits from a current rate (for example, thefull-rate) to a lower transmit data rate (for example, to the half-rate,quarter-rate, eighth-rate or even the zero-rate), thereby reducing thetransmit power P_(T) of the modem relative to when the modem wastransmitting at the full-rate. Therefore, rate-limiting in response toeither of the over-limit conditions described above is a form of modemself power-limiting, whereby the modem maintains its transmit powerP_(T) below the transmit power limit P_(L). Also, theover-limit/rate-limiting condition, as reported in status report 500,indicates to controller 214 that the requested power P_(R), or theactual transmit power P_(T) in the alternative arrangement, is greaterthan or equal to the transmit power limit P_(L). It should beappreciated that while the modem may be operating at the zero-rate inthe transmit (that is, reverse link) direction, because it either israte-limiting (for example, in step 610) or has no payload data totransmit (step 608), it may still receive full-rate data frames in thereceive (that is, forward link) direction.

Although it can be advantageous for the modem to self rate-limit inresponse to the over-limit condition, an alternative arrangement of themodem does not rate-limit in this manner. Instead, the modem reports theover-limit condition to controller 214, and then waits for thecontroller to impose rate-limiting adjustments. A preferred arrangementuses both approaches. That is, the modem self rate-limits in response tothe over-limit condition, and the modem reports the over-limit conditionto controller 214, and in response, the controller imposes rate-limitingadjustments on the modem.

After both step 608 and step 610, the modem generates a status report(for example, status report 500) at a step 612, and provides the reportto controller 214 over a respective one of data links 218.

V. Fixed Transmit Power Limit Embodiments

FIG. 7 is a flowchart of an example method performed by MWT 206, inaccordance with the present embodiments. Method 700 includes aninitializing step 702. Step 702 includes further steps 704, 706, and708. At step 704, controller 214 establishes an individual transmitpower limit P_(L) in each of modems 216. The transmit power limits arefixed over time in method 700.

At step 706, controller 214 establishes a data call over each of modems216. In other words, a communication link, including both forward andreverse links, is established between each of the modems 216 and theremote station. The communication links operate concurrently with oneanother. In an exemplary arrangement of the present invention, thecommunication links are CDMA based communication links.

In the embodiments, a modem may be designated as an active modem or asan inactive modem. Controller 214 can schedule active modems, but notinactive modems, to transmit payload data. Controller 214 maintains alist identifying currently active modems. At a step 708, controller 214initially designates all of the modems as being active, by adding eachof the modems to the active list, for example.

At a next step 710, assuming controller 214 has received data that needsto be transmitted to the remote station, controller 214 schedules eachof the active modems to transmit payload data. In a first past throughstep 710, all of modems 216 are active (from step 708). However, insubsequent passes through step 710, some of modems 216 may be inactive,as will be described below.

Controller 214 maintains a queue of data-to-be-transmitted for each ofthe active modems, and supplies each data queue with data received fromthe external data sources over link 210. Controller 214 provides datafrom each data queue to the respective active modem. Controller 214executes data-loading algorithms to ensure the respective data queuesare generally, relatively evenly loaded, so that each active modem isconcurrently provided with data-to-be-transmitted. After controller 214provides data to each modem, each modem in turn attempts to transmit thedata in data frames at the full-rate and in accordance with therespective requested transmit power P_(R), as described above inconnection with FIG. 6.

At step 710, controller 214 also de-schedules inactive modems bydiverting data-to-be-transmitted away from such inactive modems andtoward the active modems. However, there are no inactive modems in thefirst pass through step 710, since all of the modems are initiallyactive after step 708, as mentioned above.

At a next step 712, controller 214 monitors the modem status reportsfrom all of the inactive and active modems.

At a next step 714, controller 214 determines whether any of the modems216 are over-limit, and thus rate-limiting, based on the modem statusreports. If controller 214 determines that one or more (that is, atleast one) of the modems are over-limit, then controller 214 deactivatesonly these over-limit modems, at a step 716. For example, controller 214can deactivate an over-limit modem by removing it from the active list.

If none of the modems are determined to be over-limit at step 714, themethod or processing proceeds to a step 718. Processing also proceeds tostep 718 after any over-limit modems are deactivated in step 716. Atstep 718, controller 214 determines whether or not any of the modemspreviously deactivated at step 716 need to be activated (that is,reactivated). Several techniques for determining whether modems shouldbe activated are discussed below. If the answer at step 718 is yes(modems need to be reactivated), then processing proceeds to a step 720,and controller 214 activates the previously deactivated modems that needto be activated, for example, by reinstating the modems on the activelist.

If none of the previously deactivated modems need to be activated, thenprocessing proceeds from step 718 back to step 710. Also, processingproceeds from step 720 to step 710. Steps 710 through 720 are repeatedover time, whereby over-limit ones of modems 216 are deactivated at step716 and then reactivated at step 718 as appropriate, and correspondinglyde-scheduled and re-scheduled at step 710.

When an over-limit modem is deactivated at step 716 (that is, becomesinactive), and remains deactivated through step 718, the modem will bede-scheduled in the next pass through step 710. In other words,controller 214 will no longer provide data to the deactivated modem.Instead, controller 214 will divert data to active modems. If it isassumed that the data call associated with the deactivated modem has notbeen torn-down (that is, terminated), then de-scheduling the modem atstep 710 will cause the deactivated modem to have no payload data totransmit, and will thus cause the modem to operate at the zero-rate andat a corresponding minimum transmit power level on the reverse link (seesteps 606 and 608, described above in connection with FIG. 6). Thiskeeps the data call alive or active on the deactivated/descheduledmodem, so the modem can still receive full-rate data frames on theforward link. When a data call associated with a modem is torn-down,that is, terminated or ended, the modem stops transmitting and receivingdata altogether.

Deactivating the over-limit modem at step 716 ultimately causes themodem to reduce its transmit data rate and corresponding transmit powerin the reverse link direction. In this manner, controller 214individually controls the modem transmit power limits (and thus modemtransmit powers), and as a result, can maintain the aggregate transmitpower of signal 230 at a level below the aggregate transmit power limitof MWT 206.

Alternative arrangements of method 700 are possible. As described above,deactivating step 716 includes deactivating an over-limit modem bydesignating the modem as inactive, for example, by removing the modemfrom the active list. Conversely, activating step 720 includesreinstating the deactivated modem to the active list. In an alternativearrangement of method 700, deactivating step 716 further includestearing-down (that is, terminating) the data call (that is, thecommunication link) associated with the over-limit modem. Also, in thisalternative arrangement, activating step 720 further includesestablishing another data call over the previously deactivated modem, sothat the modem can begin to transmit data to and receive data from theremote station.

In another alternative arrangement of method 700, deactivating step 716further includes deactivating all of the modems, whether over-limit ornot over-limit, when any one of the over-limit modems is detected atstep 714. In this arrangement, deactivating the modems may includedesignating all of the modems as inactive, and may further includetearing-down all of the data calls associated with the modems.

FIG. 8 is a flowchart expanding on transmit limit establishing step 704of method 700. At a first step 802, controller 214 derives the transmitpower limit for each of modems 216. For example, controller 214 maycalculate the transmit power limits, or simply access predeterminedlimits stored in a memory look-up table. At a next step 804, controller214 provides each of the modems 216 with a respective one of thetransmit power limits, and in response, the modems store theirrespective transmit power limits in their respective memories.

FIG. 9 is a flowchart expanding on determining step 718 of method 700.Controller 214 monitors (at step 712, for example) the respectivereported transmit powers of the deactivated/inactive modems that aretransmitting at the zero-rate. At a step 902, controller 214 derives,from the reported modem transmit powers, respective extrapolated modemtransmit powers representative of when the modems transmit at themaximum transmit data rate.

At a next step 904, controller 214 determines whether each extrapolatedtransmit power is less than the respective modem transmit power limitP_(L). If yes, then processing proceeds to step 720 where the respectivemodem is activated, because it is likely the modem will not exceed thepower limit. If not, the modem remains deactivated, and the methodproceeds back to step 710.

FIG. 10 is a flowchart of another example method 1000 performed by MWT206. Method 1000 includes many of the method steps described previouslyin connection with FIG. 7, and such method steps will not be describedagain. However, method 1000 includes a new step 1004 following step 716,and a corresponding determining step 1006. At step 1004, controller 214initiates an activation timeout period (for example, using timer 217)corresponding to each modem deactivated at step 716. Alternatively,controller 214 can schedule a future activation time/event correspondingto each modem deactivated in step 716.

At determining step 1006, controller 214 determines whether it is timeto activate any of the previously deactivated modems. For example,controller 214 determines whether any of the activation timeout periodshave expired, thereby indicating it is time to activate thecorresponding deactivated modem. Alternatively, controller 214determines whether the activation time/event scheduled at step 1004 hasarrived.

Alternative arrangements of method 1000, similar to the alternativearrangements discussed above in connection with method 700, are alsoenvisioned.

VI. Fixed Transmit Power Limit Arrangements

1. Uniform Limits

In one fixed limit arrangement, a uniform set of fixed transmit powerlimits is established across all of modems 216. That is, each modem hasthe same transmit power limit as each of the other modems. FIG. 11 is anexample plot of Power versus Modem index(i) identifying respective onesof the modems 216, wherein uniform, modem transmit power limits P_(Li)are depicted. As depicted in FIG. 11, modem(1) corresponds to powerlimit P_(L1), modem(2) corresponds to power limit P_(L2), and so on.

In one arrangement of uniform limits, each transmit power limit P_(L) isequal to the aggregate transmit power limit APL divided by the totalnumber N of modems 216. Under this arrangement of uniform limits, whenall of the modems have respective transmit powers equal to theirrespective transmit power limits, the aggregate transmit power for allof the modems will just meet, and not exceed, the APL. An example APL inthe present invention is approximately 10 or 11 decibel-Watts (dBW).

FIG. 11 also represents an example transmit scenario for MWT 206.Depicted in FIG. 11 are representative, requested modem transmit powersP_(R1) and P_(R2) corresponding to modem(1) and modem(2). The exampletransmit scenario depicted in FIG. 11 corresponds to the scenario inwhich all of the requested modem transmit powers are below therespective, uniform transmit power limits. In this situation, none ofthe modems are over-limit, and thus rate-limiting.

FIG. 12 is another example transmit scenario similar to FIG. 11, exceptthat modem(2) has a requested power P_(R2) exceeding respective transmitpower limit P_(L2). Therefore, modem(2) is over-limit, and thusrate-limiting. Since modem(2) is over-limit, controller 214 deactivatesmodem(2) in accordance with method 700 or method 1000, thereby causingmodem(2) to transmit at a zero-data rate, and at a correspondinglyreduced transmit power level 1202.

2. Tapered Limits

FIG. 13 is an illustration of an alternative, tapered arrangement forthe fixed modem transmit power limits. As depicted, the taperedarrangement includes progressively decreasing transmit power limitsP_(Li) in respective successive ones of the N modems, where i=1 . . . N.For example, transmit power limit P_(L1) for modem(l) is less thantransmit power limit P_(L2) for modem(2), which is less than transmitpower limit P_(L3), and so on down the line.

In one tapered arrangement, each of the transmit power limits P_(Li) isequal to the APL divided by the total number of modems having transmitpower limits greater than or equal to P_(Li). For example, transmitpower limit P_(L5) is equal to the APL divided by five (5), which is thenumber of modems having transmit power limits greater than or equal toP_(L5). In another tapered arrangement, each transmit power limit P_(Li)is equal to the transmit power limit mentioned above (that is, the APLdivided by the total number of modems having transmit power limitsgreater than or equal to P_(Li)) less a predetermined amount, such asone, two or even three decibels (dB). This permits a safety margin inthe event that the modems tend to transmit at an actual transmit powerlevel that is slightly higher than the respective transmit power limits,before they are deactivated.

Assume a transmit scenario where all of the modems transmit atapproximately the same power, and all of the transmit powers areincreasing over time. Under the tapered arrangement, modem(N)rate-limits first, modem(N-1) rate limits next, modem(N-2) rate-limitsthird, and so on. In response, controller 214 deactivates/deschedulesmodem(N) first, modem(N-1) second, modem(N-3) third, and so on.

VII. Modem Calibration—Determining Gain Factors g(i)

As described above in connection with FIG. 2, each modem 216 i generatesa transmit signal 222 i _(T) having a respective transmit power level.Also, each modem 216 i generates a status report including a modemtransmit power estimate P_(Rep)(i) of the respective transmit powerlevel. Each modem transmit signal 222 i _(T) traverses a respectivetransmit path from modem 222 i to the output of transmit amplifier 228.The respective transmit path includes RF connections, such as cables andconnectors, power combiner/splitter assembly 220, and transmit amplifier228. Therefore, transmit signal 222 i _(T) experiences a respective netpower gain or loss g(i) along the respective transmit path. An examplegain for the above-mentioned transmit path is approximately 29 dB.

Accordingly, the gain or loss g(i) of the respective transmit path maycause the power level of respective transmit signal 222 i _(T) at theoutput of modem 222 i to be different from the transmit power level atthe output of transmit amplifier 228. Therefore, the respective modemtransmit power estimate P_(Rep)(i) may not accurately represent therespective transmit power at the output of transmit amplifier 228. Amore accurate estimate P_(O)(i) of the transmit power at the output oftransmit amplifier 228 (due to modem 222 i), is the reported powerP_(Rep)(i) adjusted by the corresponding gain/loss amount g(i).Therefore, g(i) is referred to as a modem dependent gain correctionfactor g(i), or the modem gain factor g(i) for modem 222 i.

When reported modem transmit power estimate P_(Rep)(i) and modem gaincorrection factor g(i) both represent power terms (as expressed indecibels or Watts, for example), the corrected transmit power estimateP_(O)(i) is given by:P _(O)(i)=g(i)+P _(Rep)(i).

Alternatively, when reported transmit power estimate P_(Rep)(i) andmodem gain correction factor g(i), in Watts, for example, the transmitpower P_(O)(i) is given by:P _(O)(i)=g(i)P _(Rep)(i).

It is useful to be able to calibrate MWT 206 dynamically, to determinethe gain correction factors g(i) corresponding to all of the N modems.Once the factors g(i) are determined, they can be used to calculate moreaccurate individual and aggregate modem transmit power estimates fromthe modem transmit power reports.

FIG. 14 is a flowchart of an example method of calibrating modems 216 inMWT 206. At a first step 1405, controller 214 schedules all N modems 216to transmit data, so as to cause all of the modems to transmit data,concurrently.

At a next step 1410, controller 214 collects status reports 500,including respective reported transmit powers P_(Rep)(i), where irepresents modem i, and i=1 . . . N.

At a next step 1420, controller 214 receives an aggregate transmit powermeasurement P_(Agg) for all of the N modems, for example, as determinedby transmit power monitor 234.

At a next step 1425, controller 214 generates an equation representingthe aggregate transmit power as a cumulative function of reportedtransmit powers P_(Rep)(i) and corresponding unknown, modem dependentgain correction factors g(i). For example, aggregate transmit powerP_(Agg) is represented as:$P_{Agg} = {\sum\limits_{i = 1}^{N_{N}}{{g(i)}{{P_{Rep}(i)}.}}}$

At a next step 1430, previous steps 1405, 1410, 1420 and 1425 arerepeated N times to generate N simultaneous equations in P_(Rep)(i) andunknown gain correction factors g(i).

At a next step 1435, controller 214 determines the N gain correctionfactors g(i) by solving the N equations generated in step 1430.Determined gain correction factors g(i) are stored in memory 215 of MWT206, and used as needed to adjust/correct modem transmit power estimatesP_(Rep)(i) in the methods of the invention, described below. Method 1400may be scheduled to repeat periodically to update factors g(i) overtime.

VIII. Methods Using Dynamically Updated Transmit Limits

FIG. 15 is a flowchart of an example method 1500 of operating MWT 206,using dynamically updated individual modem transmit power limits. Inmethod 1500, controller 214 initializes (step 702), schedules anddeschedules active and inactive ones of modems 216 (step 710), andmonitors status reports from the modems (step 712), as described above.At a next step 1502, controller 214 determines whether to modify (forexample, increase or decrease) or maintain the number of active modemsof MWT 206, in order to maximize an aggregate reverse link data rate(that is, the aggregate transmit data rate) without exceeding theaggregate transmit power limit of the MWT.

At a next step 1504, controller 214 increases, decreases, or maintainsthe number of active modems, as necessary, in accordance with step 1502.To increase the number of active modems, controller 214 adds one or morepreviously inactive modems to the active list. Conversely, to decreasethe number of active modems, controller 214 deletes one or morepreviously active modems from the active list.

At a next step 1506, controller 214 updates/adjusts individual transmitpower limits in at least some of modems 216, as necessary. Techniquesfor adjusting individual transmit power limits will be described furtherbelow. In step 1506, the individual transmit power limits are adjustedacross modems 216 such that when all of the individual transmit limitsare combined together into a combined transmit power limit, the combinedtransmit power limit does not exceed the aggregate transmit power limitof MWT 206. Exemplary transmit power limit arrangements that may be usedwith method 1500 are described later in connection with Table 1 and FIG.19. A reason for varying modem transmit power limits in method 1500 isto avoid rate-limiting conditions in the modems. Also, a reason fordeactivating modems (that is, decreasing the number of active modems)includes avoiding rate-limiting conditions so as to increase the overalltransmit data rate on the reverse-link while operating under theaggregate transmit power limit.

At first blush, it might appear that deactivating modems would decrease,not increase, the transmit data rate. However, operating a number ofmodems, for example, 16 modems, at their rate-limited data rates (forexample, at 4800 bps) achieves a lower effective data rate thanoperating a lesser number modems, for example 8 modems, at their fullrates (for example, 9600 bps), even though each case may have the sameaggregate transmit power. This is because the ratio of overheadinformation (used to manage the data calls, for example) toactual/useful data (used by end users, for example) is disadvantageouslygreater for rate limiting modems compared to non-rate limiting modems.

FIG. 16 is a flowchart of an example method 1600 expanding on method1500. Method 1600 includes a step 1602 expanding on step 1502 of method1500. Step 1602 includes further steps 1604 and 1606. At step 1604,controller 214 determines a maximum number N_(Max) of active modems thatcan concurrently transmit at their respective maximum data rates (forexample, at 9600 bps), without exceeding the aggregate transmit powerlimit of MWT 206. It is assumed that N_(Max) is less than or equal to atotal number N of modems 216.

At next step 1606, controller 214 compares the maximum number N_(Max) toa number M of previously active modems (that is, the number of activemodems used in a previous pass through step 710, described above).

A next step 1610, corresponding to step 1504 of method 1500, includesfurther steps 1612, 1614 and 1616. If the maximum number N_(Max) ofactive modems from step 1604 is greater than the number M of previouslyactive modems, then the method proceeds from step 1606 to next step1612. At step 1612, controller 214 increases the number M of activemodems to the maximum number N_(Max) of active modems. To do this,controller 214 selects an inactive modem to activate from among the Nmodems.

Alternatively, if the maximum number N_(Max) of modems is less than M,then processing proceeds from step 1606 to step 1614. At step 1614,controller 214 decreases the number of active modems. To do this,controller 214 selects an active modem to deactivate. Steps 1612 and1614 together represent an adjusting step (also referred to as amodifying step) where the number M of previously active modems ismodified in preparation for a next pass through steps 710, 712, and soon.

Alternatively, if the maximum number N_(Max) is equal to M, thenprocessing proceeds from step 1606 to step 1616. In step 1616,controller 214 simply maintains the number of active modems at M, forthe next pass through steps 710, 712, and so on.

The method proceeds from both modifying steps 1612 and 1614 to a next,limit adjusting step 1620. At step 1620, controller 214 increases theindividual transmit power limits in the one or more modems that wereactivated at step 1612. Conversely, controller 214 decreases theindividual power limits in the one or more modems that were deactivatedin step 1614.

The method proceeds from steps 1610 and 1620 back toscheduling/descheduling step 710, and the process described aboverepeats.

FIG. 17 is a flowchart of an example method 1700 of determining themaximum number N_(Max) of active modems using an averageenergy-per-transmitted-bit of the N modems. Method 1700 expands on step1604 of method 1600. At a first step 1702, controller 214 determines anaggregate transmit data rate based on the respective transmit data ratesreported by the N modems. For example, controller 214 adds together allof the transmit data rates reported by the N modems in respective statusreports 500.

At a next step 1704, controller 214 determines an aggregate power levelof transmit signal 230, at the output of transmit amplifier 228. Forexample, controller 214 may receive transmit power measurements (signal236) from transmit power monitor 234. Alternatively, controller 214 mayaggregate individual modem transmit power estimates P_(Rep)(i) (ascorrected using factors g(i)) received from the individual modems inrespective status reports 500.

At a next step 1706, controller 214 determines the averageenergy-per-transmitted-bit across the N modems 216 based on theaggregate data rate and the aggregate transmit power. In one arrangementof the embodiments, controller 214 determines the averageenergy-per-transmitted-bit in accordance the following relationships:BE _(b) _(—) _(avg) =P(t)Δt=E _(T),and, therefore,E _(b) _(—) _(avg)=(P(t)Δt)/B=E _(T) /B,where:

-   Δt is a predetermined measurement time interval (for example, the    duration of a transmitted frame, such as 20 ms),-   B is the aggregate data rate during time interval Δt,-   E_(b) _(—) _(avg) is the average energy-per-transmitted-bit during    time interval Δt,-   P(t) is the aggregate transmit power during time interval Δt, and-   E_(T) is the total energy of all the bits transmitted during time    interval Δt.

At a next step 1708, controller 214 determines the maximum numberN_(Max) based on the average energy-per-transmitted-bit and theaggregate transmit power limit. In one arrangement, controller 214determines the maximum number N_(Max) in accordance with the followingequations:((R _(max) N _(Max) +R _(min)(N−N _(Max)))E _(b) _(—) _(avg) =APL,and, therefore,N _(Max)=((APL/E _(b) _(—) _(avg))−P _(min) N)/(R _(max) −R _(min)),where:

-   APL is the aggregate transmit power limit of MWT 206 (for example,    10 or 11 decibel-Watts (dBW)),-   R_(max) is a maximum data rate of the N modems (for example, 9600    bps),-   R_(min) is a minimum data rate of the N modems (for example, 2400    bps),-   E_(b) _(—) _(avg) is the average energy-per-transmitted-bit during    time interval Δt,-   N is the total number of modems 216, and-   N_(Max) is the maximum number of active modems to be determined.

FIG. 18 is a flowchart of an example method 1800 of determining themaximum number N_(Max) of active modems, using an individualenergy-per-transmitted-bit for each of modems 216. Method 1800 expandson step 1604 of method 1600. At a first step 1802, controller 214determines an individual energy-per-transmitted-bit E_(b)(i) for eachmodem using modem reports 500. In one arrangement of the embodiment,controller 214 determines each energy-per-transmitted-bit E_(b)(i) inaccordance the following relationship:E _(b)(i)=g(i)P _(Rep)(i)Δt/Bi,where:

-   Δt is a predetermined measurement time interval,-   E_(b)(i) is the individual energy-per-transmitted-bit for modem i,    where i=1 . . . N, over time interval Δt,-   P_(Rep)(i) is a reported modem transmit power (that is, a transmit    power estimate for modem i), and-   g(i) is a modem dependent gain correction factor, also referred to    as a gain calibration factor (described above in connection with    FIG. 14), and-   Bi is the transmit data rate of modem i.

At a step 1804, controller 214 sorts the modems according to theirrespective energy-per-transmitted-bits E_(b)(i).

At a next step 1805, controller 214 determines the maximum numberN_(Max) of active modems based on the individual modemenergy-per-transmitted-bits, using an iterative process. In onearrangement, the iterative process of step 1805 determines the maximumnumber N_(Max) of active modems that can be supported, using thefollowing equation:${{APL} = {{\sum\limits_{i = 1}^{N_{Max}}{P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{Max}}^{N}{P_{\min}{E_{b}(i)}}}}},$where:

-   APL is the aggregate transmit power limit,-   P_(max) is the maximum data rate for each modem,-   P_(min) is the minimum data rate for each modem, and-   E_(b)(i) is the individual energy-per-transmitted-bit for modem i.

Step 1805 is now described in further detail. A step 1806 within step1805 is an initializing step in the iterative process, wherein modem 214sets a test number N_(Act) of active modems equal to one (1). Testnumber N_(Act) represents a test, maximum number of active modems. At anext step 1808, modem 214 determines an expected transmit power P_(Exp)using the test number N_(Act) of modems. In step 1808, it is assumedthat the test number N_(Act) of modems having the-lowest individualenergy-per-transmitted-bits among the N modems each transmit at amaximum data rate (for example, 9600 bps). In the arrangement mentionedabove, step 1808 determines the expected transmit power in accordancewith the following relationship:${P_{Exp} = {{\sum\limits_{i = 1}^{N_{act}}{P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{act}}^{N}{P_{\min}{E_{b}(i)}}}}},$

At a next step 1809, controller 214 compares the expected transmit powerP_(Exp) to the APL. If P_(Exp)<APL, then more active modems can besupported. Thus, the test number N_(Act) of active modems is incremented(step 1810), and the method proceeds back to step 1808.

Alternatively, if P_(Exp)=APL, then the maximum number N_(Max) of activemodems is set equal to the present test number N_(Act) (step 1812).

Alternatively, if P_(Exp)>APL, then the maximum number N_(Max) is setequal to the previous test number of active modems, that is, N_(Act)−1(step 1814).

If P_(Exp) is neither equal to nor greater than APL then the processreturns to step 1810 and step 1809. At some point a maximum number ofmodems may be reached or exceeded and either step 1812 or 1814,respectively, are reached. The process for recalculating APL checkingthe current N (number of access terminals in use), or checking P_(Exp)relative to APL, may be repeated every so often or on a periodic basisas part of an iterative procedure to prevent overdriving the poweramplifier.

IX. Example Transmit Power Limits

Table 1, below, includes exemplary modem transmit power limits that maybe used in the present invention. TABLE 1 A No. active B C D modemsActive Modem Active Modem Active Modem (Total Limits (dBm) Limits (dBm)Limits (dBm) N = 16) APL = 10 dBW APL = 11 dBW APL = 10 dBW 1.0 5.0 5.24.2 2.0 5.0 4.6 3.6 3.0 5.0 4.0 3.0 4.0 5.0 3.5 2.5 5.0 4.0 3.1 2.1 6.03.2 2.7 1.7 7.0 2.5 2.3 1.3 8.0 2.0 2.0 1.0 9.0 1.5 1.7 0.7 10.0 1.0 1.40.4 11.0 0.6 1.1 0.1 12.0 0.2 0.9 −0.1 13.0 −0.1 0.6 −0.4 14.0 −0.5 0.4−0.6 15.0 −0.8 0.2 −0.8 16.0 −1.0 0.0 −1.0

The transmit power limits of Table 1 may be stored in memory 215 of MWT206. Table 1 assumes MWT 206 includes a total of N=16 modems. Each rowof table 1 represents a corresponding number (such as 1, 2, 3, and soon, down the rows) of active ones of the N modems, at any given time.Each row of Column A identifies a given number of active modems. Thenumber of inactive modems corresponding to any given row of Table 1 isthe difference between the total number of modems (16) and the number ofactive modems specified in the given row.

Columns B, C and D collectively represent three different individualtransmit power limit arrangements of the present invention. The transmitlimit arrangement of column B assumes an APL of 10 dBW in MWT 206. Also,the arrangement of column B assumes that, in any given row, all of theactive modems receive a common maximum transmit limit, while all of theinactive modems receive a common minimum transmit limit equal to zero.For example in column B, when the number of active modems is six (6), acommon maximum transmit limit of 3.2 decibel-milliwatt (dBm) isestablished in each of the active modems, and a common minimum transmitlimit of zero is established in each of the ten (10) inactive modems.The sum of the maximum transmit power limits in all of the active modemscorresponding to any given row is equal to the APL.

The transmit limit arrangement of column C assumes an APL of 11 dBW inMWT 206. Also, the arrangement of column C assumes that, for any givennumber of active modems (that is, for each row in Table 1), all of theactive modems receive a common maximum transmit limit, while all of theinactive modems receive a common minimum transmit limit equal to themaximum transmit limit less six (6) dB. For example in column C, whenthe number of active modems is six (6), a maximum transmit limit of 2.7dBm is established in each of the six (6) active modems, and a minimumtransmit limit of (2.7-6) dBm is established in each of the ten (10)inactive modems. The sum of the maximum transmit power limits in all ofthe active modems, together with the sum of the minimum transmit powerlimits in all of the inactive modems, corresponding to any given row isequal to the APL. Since the transmit power limit in each of the inactivemodems is greater than zero, the inactive modems may be able to transmitat respective minimum data rates, or at least at the zero-data rate, inorder to maintain their respective data links active.

The transmit limit arrangement of column D is similar to that of columnC, except a lower APL of 10 dBW is assumed in the arrangement of columnD. The arrangement of column D assumes that, for any given number ofactive modems (that is, for each row in Table 1), all of the activemodems receive a common maximum transmit limit, while all of theinactive modems receive a common minimal transmit limit equal to themaximum transmit limit less six (6) dB. For example, from column D, whenthe number of active modems is six (6), a maximum transmit limit of 1.7dBm is established in each of the active modems, and a transmit limit of(1.7-6) dBm is established in each of the ten (10) inactive modems.

Controller 214 can use the limits specified in Table 1 to establish andadjust individual transmit limits in modems 216 in methods 1500 and1600, described above in connection with FIGS. 15 and 16. For example,assume the transmit limit arrangement of Table 1, column D, is beingused with method 1600. Assume the number of active modems in a previouspass through step 710 is seven. During the previous pass, a transmitlimit of 1.3 dBm is established in each of the seven active modems, anda transmit limit of (1.3-6) dBm is established in the other nine,inactive modems (see the entry in column D corresponding to seven activemodems). Also assume that in the next pass through steps 1602 and 1614,the number of active modems is decreased from seven down to six. Then,at limit adjusting step 1620, a new transmit limit of 1.7 dB isestablished in each of the six active modems, and a transmit limit of(1.7-6) dB is established in each of the ten remaining inactive modems.

FIG. 19 is a graphical representation of the information presented inTable 1. FIG. 19 is a plot of transmit limit power (in dBm) versus thenumber of active modems (labeled as N) for each of the transmit limitarrangements listed in columns B, C and D of Table 1. In FIG. 19, thetransmit limit arrangement of column B is represented by a curve COL B,the limit arrangement of column C is represented by a curve COL C, andthe limit arrangement of column D is represents by a curve COL D.

X. MWT Computer Controller

FIG. 20 is a functional block diagram of an example controller (whichcan also be a plurality of controllers) 2000 representing controller214. Controller 2000 includes a series of controller modules forperforming the various method steps of the embodiments discussed above.

A scheduler/descheduler 2002 schedules active modems to transmit payloaddata, and de-schedules inactive modems; a call manager 2004 establishesdata calls and tears-down data calls over the plurality of modems 216;and a status monitor 2006 monitors status reports from modems 216, forexample, to determine when various ones of the modems are over-limit,and to collect modem transmit data rates and transmit powers. Statusmonitor 2006 may also determine an aggregate data rate and an aggregatetransmit power based on the modem reports.

A deactivator/activator module 2008 acts to deactivate over-limit ones(in the fixed limit arrangement of the present invention) of the modems(for example by removing the modems from the active list) and toactivate deactivated ones of the modems by reinstating the modems on theactive list. Module 2008 also activates/deactivates selected ones of themodems in accordance with steps 1504, 1612, and 1614 of methods 1500 and1600.

A limit calculator 2010 operates to calculate/derive transmit powerlimits for each of the modems 216. Limit calculator also accessespredetermined transmit power limits stored in memory 215, for example.

An initializer 2012 supervises/manages initialization of the system,such as establishing initial transmit power limits in each modem,setting up calls over each modem, initializing various lists and queuesin MWT 206, and so on.

A modem interface 2014 receives data from and transmits data to modems216, and a network interface 2016 receives and transmits data overinterface 210.

A module 2020 determines whether to modify the number of active modemsin accordance with steps 1502 and 1602 of methods 1500 and 1600. Module2020 includes a sub-module 2022 for determining a maximum number ofactive modems that can be supported based on either anaverage-energy-per-transmitted-bit or individual modemenergy-per-transmitted-bits. Sub-module 2022 includes comparison orcomparing logic (such as a comparator) configured to operate inaccordance with comparing step 1606 of method 1600. Module 2020 alsoincludes sub-modules 2024 and 2026 for determining theaverage-energy-per-transmitted-bit and the individual modemenergy-per-transmitted-bits, respectively. Sub-modules 2024 and 2026, oralternatively, status monitor 2006, also determine an aggregate datarate and an aggregate transmit power based on modem reports.

A calibration module 2040 controls calibration in MWT 206 in accordancewith method 1400, for example. The calibration module includes anequation generator to generate simultaneous equations and an equationsolver to solve the equations to determine modem correction factorsg(i). The calibration module can also call/incorporate other modules, asnecessary, to perform calibration of MWT 206.

A software interface 2050 is used for interconnecting all of the abovementioned modules to one another.

Features of the present invention can be performed and/or controlled byprocessor/controller 214, which in effect comprises a programmable orsoftware-controllable element, device, or computer system. Such acomputer system includes, for example, one or more processors that areconnected to a communication bus. Although telecommunication-specifichardware can be used to implement the present invention, the followingdescription of a general purpose type computer system is provided forcompleteness.

The computer system can also include a main memory, preferably a randomaccess memory (RAM), and can also include a secondary memory and/orother memory. The secondary memory can include, for example, a hard diskdrive and/or a removable storage drive. The removable storage drivereads from and/or writes to a removable storage unit in a well knownmanner. The removable storage unit, represents a floppy disk, magnetictape, optical disk, and the like, which is read by and written to by theremovable storage drive. The removable storage unit includes a computerusable storage medium having stored therein computer software and/ordata.

The secondary memory can include other similar means for allowingcomputer programs or other instructions to be loaded into the computersystem. Such means can include, for example, a removable storage unitand an interface. Examples of such can include a program cartridge andcartridge interface (such as that found in video game devices), aremovable memory chip (such as an EPROM, or PROM) and associated socket,and other removable storage units and interfaces which allow softwareand data to be transferred from the removable storage unit to thecomputer system.

The computer system can also include a communications interface. Thecommunications interface allows software and data to be transferredbetween the computer system and external devices. Software and datatransferred via the communications interface are in the form of signalsthat can be electronic, electromagnetic, optical or other signalscapable of being received by the communications interface. As depictedin FIG. 2, processor 214 is in communications with memory 215 forstoring information. Processor 214, together with the other componentsof MWT 206 discussed in connection with FIG. 2, performs the methods ofthe present invention.

In this document, the terms “computer program medium” and “computerusable medium” are used to generally refer to media such as a removablestorage device, a removable memory chip (such as an EPROM, or PROM)within MWT 206, and signals. Computer program products are means forproviding software to the computer system.

Computer programs (also called computer control logic) are stored in themain memory and/or secondary memory. Computer programs can also bereceived via the communications interface. Such computer programs, whenexecuted, enable the computer system to perform certain features of thepresent invention as discussed herein. For example, features of the flowcharts depicted in FIGS. 7, 8, 9 and 10, can be implemented in suchcomputer programs. In particular, the computer programs, when executed,enable processor 214 to perform and/or cause the performance of featuresof the present invention. Accordingly, such computer programs representcontrollers of the computer system of MWT 206, and thus, controllers ofthe MWT.

Where the embodiments are implemented using software, the software canbe stored in a computer program product and loaded into the computersystem using the removable storage drive, the memory chips or thecommunications interface. The control logic (software), when executed byprocessor 214, causes processor 214 to perform certain functions of theinvention as described herein.

Features of the invention may also or alternatively be implementedprimarily in hardware using, for example, a software-controlledprocessor or controller programmed to perform the functions describedherein, a variety of programmable electronic devices, or computers, amicroprocessor, one or more digital signal processors (DSP), dedicatedfunction circuit modules, and hardware components such as applicationspecific integrated circuits (ASICs) or programmable gate arrays (PGAs).Implementation of the hardware state machine so as to perform thefunctions described herein will be apparent to persons skilled in therelevant art(s).

The previous description of the preferred embodiments is provided toenable a person skilled in the art to make or use the present invention.While the invention has been particularly shown and described withreference to embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention.

XI. CONCLUSION

The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed. Any such alternate boundaries are thus within the scope andspirit of the claimed invention. One skilled in the art will recognizethat these functional building blocks can be implemented by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or many combinationsthereof. Thus, the breadth and scope of the present invention should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A method of operating a wireless device within an aggregate transmitpower limit, the wireless device including N wireless modems havingtheir respective transmit outputs combined to produce an aggregatetransmit output, comprising: (a) scheduling a plurality, M, of activeones of the N modems to transmit payload data, where M is less than orequal to N; (b) monitoring status reports from at least the activemodems; (c) determining, based on the status reports, whether to modifythe number of active modems in order to maximize an aggregate transmitdata rate of the N modems while maintaining an aggregate transmit powerof the N modems at or below the aggregate transmit power limit; and (d)modifying the number of active modems when it is determined in step (c)that the number of active modems should be modified to maintain theaggregate transmit power level of the N modems at or below the aggregatetransmit power level.
 2. The method of claim 1, wherein step (d)comprises modifying the number of active modems to a modified number ofactive modems when it is determined that the number of active modemsshould be modified, the method further comprising: (e) repeating steps(a), (b), and (c) for the modified number of active modems.
 3. Themethod of claim 1, wherein step (c) comprises: (c)(i) determining amaximum number of active modems that can concurrently transmit data,each at a predetermined maximum data rate, while maintaining theaggregate transmit power of the N modems at or below the aggregatetransmit power limit; and (c)(ii) comparing the maximum number of activemodems to the number M of active modems.
 4. The method of claim 3,wherein step (c)(i) comprises: determining an averageenergy-per-transmitted-bit across at least the M active modems; anddetermining the maximum number of active modems based on the averageenergy-per-transmitted-bit and the aggregate transmit power limit. 5.The method of claim 4, wherein the status reports monitored in step (b)indicate a respective transmit data rate for each of the N modems, saidstep of determining the average energy-per-transmitted-bit comprising:determining an aggregate transmit data rate across the N modems based ontheir respective transmit data rates; determining the aggregate transmitpower; and determining the average energy-per-transmitted-bit based onthe aggregate transmit data rate and the aggregate transmit power. 6.The method of claim 3, wherein step (c)(i) comprises: determining anindividual energy-per-transmitted-bit for each of the N modems; anddetermining the maximum number of active modems based on the individualenergy-per-transmitted-bits and the aggregate transmit power limit. 7.The method of claim 6, wherein the status reports monitored in step (b)indicate a respective transmit power for each of the N modems, said stepof determining the individual energy-per-transmitted-bit comprisingdetermining the individual energy-per-transmitted-bit for each of the Nmodems based on the respective transmit power.
 8. The method of claim 6,further comprising: selecting as next active modems the maximum numberof modems having the lowest individual energy-per-transmitted-bits amongthe N modems; and repeating step (a) using the next active modems. 9.The method of claim 3, wherein step (d) comprises increasing the numberof active modems to the maximum number when the maximum number isgreater than M.
 10. The method of claim 3, wherein step (d) comprisesdecreasing the number of active modems to the maximum number when themaximum number is less than M.
 11. The method of claim 1, furthercomprising: prior to step (a), establishing a respective transmit powerlimit for each of the N modems to limit the respective transmit powersof each of the N modems, wherein all of the transmit power limits, whencombined, represent a combined transmit power limit that is less than orequal to the aggregate transmit power limit.
 12. The method of claim 1,wherein: a respective transmit power limit is established in each of theN modems to limit the respective transmit powers of each of the Nmodems; step (d) comprises activating a selected, previously inactiveone of the N modems, thereby increasing the number of active modems; andthe method further comprises increasing the respective transmit powerlimit in the selected one of the N modems.
 13. The method of claim 1,wherein: a respective transmit power limit is established in each of theN modems to limit the respective transmit powers of each of the Nmodems; step (d) comprises deactivating a selected, previously activeone of the N modems, thereby decreasing the number of active modems; andthe method further comprises decreasing the respective transmit powerlimit in the selected one of the N modems.
 14. The method of claim 1,further comprising: prior to step (a), establishing an individualcommunication link between a remote station and each of the N modems,each communication link including a forward link and a reverse link,whereby each modem is able to transmit data in the reverse linkdirection and receive data in the forward link direction; andmaintaining all of the communication links during steps (a), (b), (c)and (d).
 15. The method of claim 14, wherein each communication link isa Code Division Multiple Access (CDMA) based communication link.
 16. Amethod of operating a wireless terminal within an aggregate transmitpower limit, the wireless terminal including N wireless modems havingtheir respective transmit outputs combined to produce an aggregatetransmit output, the method comprising: (a) determining an averageenergy-per-transmitted-bit across a plurality of previously active onesof the N modems that were previously transmitting; (b) determining,based on the average energy-per-transmitted-bit and the aggregatetransmit power limit, a maximum number of active modems that canconcurrently transmit data at a maximum data rate without exceeding themaximum aggregate transmit power limit; and (c) schedulingdata-to-be-transmitted over the determined maximum number of activemodems.
 17. The method of claim 16, further comprising: prior to step(a): determining an aggregate transmit power of the N modemscorresponding to when the plurality of active modems were previouslytransmitting data; monitoring status reports from the N modems, thestatus reports indicating a respective transmit data rate for each ofthe N modems; and determining, based on the respective transmit datarates, an aggregate data rate of the N modems corresponding to theaggregate transmit power; and wherein step (a) comprises determining theaverage energy-per-transmitted-bit based on the aggregate transmit powerand the aggregate data rate.
 18. The method of claim 16, wherein: eachof the N modems is adapted to transmit data at at least one of a maximumtransmit data rate and a minimum transmit data rate; and step (b)comprises determining the maximum number of active modems based on theminimum and maximum transmit data rates as well as the averageenergy-per-transmitted-bit and the aggregate transmit power limit. 19.The method of claim 16, comprising: repeating steps (a), (b) and (c)periodically, thereby causing the maximum of active modems to vary overtime in correspondence with the average energy-per-transmitted bit. 20.A method of operating a wireless terminal within an aggregate transmitpower limit, the wireless terminal including N wireless modems havingtheir respective transmit outputs combined to produce an aggregatetransmit output, the method comprising: (a) determining an individualenergy-per-transmitted-bit for each of the N modems that was previouslytransmitting; (b) determining, based on all of the individualenergy-per-transmitted-bits and the aggregate transmit power limit, amaximum number of active modems that can concurrently transmit data at amaximum data rate without exceeding the aggregate transmit power limit;and (c) scheduling the maximum number of active modems to transmit data.21. The method of claim 20, further comprising: prior to step (c),sorting the N modems according to their respective individualenergy-per-transmitted-bits; and wherein step (c) comprises schedulingthe maximum number of active modems having the lowest individualenergy-per-transmitted-bits among the N modems.
 22. The method of claim20, further comprising, prior to step (a), monitoring status reportsfrom at least the active modems, the status reports collectivelyincluding a transmit power estimate of each active modem, wherein step(a) comprises determining, from each transmit power estimate, thecorresponding individual energy-per-transmitted-bit.
 23. A method ofdynamically calibrating a wireless terminal including N wireless modemshaving their respective transmit outputs combined to produce anaggregate transmit output, the method comprising: (a) scheduling each ofthe N modems to concurrently transmit respective data, thereby causingeach of the N modems to concurrently transmit; (b) receiving respectivereported transmit powers P_(Rep)(i) from the N modems corresponding towhen the N modems concurrently transmit, where i designates a respectivemodem from 1 to N; (c) measuring, at the aggregate transmit output, anaggregate transmit power P_(Agg) of the N modems corresponding to whenthe N modems concurrently transmit; (d) generating an equationrepresenting the aggregate transmit power as a cumulative function ofeach reported transmit power P_(Rep)(i) and a corresponding,undetermined, modem dependent gain factor g(i); (e) repeating steps (a),(b), (c) and (d) N times to generate N simultaneous equations; and (f)determining all of the modem dependent gain factors from the Nsimultaneous equations.
 24. The method of claim 23, further comprising:repeating steps (a) through (f) periodically, whereby the modemdependent gain factors are updated periodically.
 25. A wireless terminalconstrained to operate under an aggregate transmit power limit, thewireless terminal including N wireless modems having their respectivetransmit outputs combined together to produce an aggregate transmitoutput, comprising: means for scheduling a plurality, M, of active onesof the N modems to transmit payload data, where M is less than or equalto N; means for monitoring status reports from at least the activemodems; means for determining, based on the status reports, whether tomodify the number of active modems in order to maximize an aggregatetransmit data rate of the N modems while maintaining an aggregatetransmit power of the N modems at or below the aggregate transmit powerlimit; and means for modifying the number of active modems when it isdetermined that the number of active modems should be modified tomaintain the aggregate transmit power level of the N modems at or belowthe aggregate transmit power level.
 26. The wireless terminal of claim25, wherein: said modifying means comprises means for modifying thenumber of active modems to an modified number of active modems when itis determined that the number of active modems should be modified; andthe scheduling means, the monitoring means, and the modifying meansrepeat their respective functions using the modified number of activemodems.
 27. The wireless terminal of claim 25, wherein the determiningmeans comprises: means for determining a maximum number of active modemsthat can concurrently transmit data, each at a predetermined maximumdata rate, while maintaining the aggregate transmit power of the Nmodems at or below the aggregate transmit power limit; and means forcomparing the maximum number of active modems to the number M of activemodems.
 28. The wireless terminal of claim 27, wherein the means fordetermining the maximum number comprises: means for determining anaverage energy-per-transmitted-bit across at least the M active modems;and means for determining the maximum number of active modems based onthe average energy-per-transmitted-bit and the aggregate transmit powerlimit.
 29. The wireless terminal of claim 28, wherein the status reportsmonitored by the monitoring means indicate a respective transmit datarate for each of the N modems, said means for determining the averageenergy-per-transmitted-bit comprising: means for determining anaggregate transmit data rate across the N modems based on theirrespective transmit data rates; means for determining the aggregatetransmit power; and means for determining the averageenergy-per-transmitted-bit based on the aggregate transmit data rate andthe aggregate transmit power.
 30. The wireless terminal of claim 27,wherein the means for determining the maximum number comprises: meansfor determining an individual energy-per-transmitted-bit for each of theN modems; and means for determining the maximum number of active modemsbased on the individual energy-per-transmitted-bits and the aggregatetransmit power limit.
 31. The wireless terminal of claim 30, wherein thestatus reports monitored by the monitoring means indicate a respectivetransmit power for each of the N modems, the means for determining theindividual energy-per-transmitted-bit comprising means for determiningthe individual energy-per-transmitted-bit for each of the N modems basedon the respective transmit power.
 32. The wireless terminal of claim 30,further comprising: means for selecting as next active modems themaximum number of modems having the lowest individualenergy-per-transmitted-bits among the N modems; and wherein the meansfor scheduling repeats its respective function using the next activemodems.
 33. The wireless terminal of claim 27, wherein the modifyingmeans comprises means for increasing the number of active modems to themaximum number when the maximum number is greater than M.
 34. Thewireless terminal of claim 27, wherein the modifying means comprisesmeans for decreasing the number of active modems to the maximum numberwhen the maximum number is less than M.
 35. The wireless terminal ofclaim 25, further comprising: means for establishing a respectivetransmit power limit for each of the N modems to limit the respectivetransmit powers of each of the N modems, wherein all of the transmitpower limits, when combined, represent a combined transmit power limitthat is less than or equal to the aggregate transmit power limit. 36.The wireless terminal of claim 25, wherein: a respective transmit powerlimit is established in each of the N modems to limit the respectivetransmit powers of each of the N modems; the modifying means comprisesmeans for activating a selected, previously inactive one of the Nmodems, thereby increasing the number of active modems; and the wirelessterminal further comprises means for increasing the respective transmitpower limit in the selected one of the N modems.
 37. The wirelessterminal of claim 25, wherein: a respective transmit power limit isestablished in each of the N modems to limit the respective transmitpowers of each of the N modems; the modifying means comprises means fordeactivating a selected, previously active one of the N modems, therebydecreasing the number of active modems; and the wireless terminalfurther comprises decreasing the respective transmit power limit in theselected one of the N modems.
 38. The wireless terminal of claim 25,further comprising: means for establishing an individual communicationlink between a remote station and each of the N modems, eachcommunication link including a forward link and a reverse link, wherebyeach modem is able to transmit data in the reverse link direction andreceive data in the forward link direction; and means for maintainingall of the communication links while the scheduling means, themonitoring means, the determining means, and the modifying means performtheir respective functions.
 39. The wireless terminal of claim 38,wherein each communication link is a Code Division Multiple Access(CDMA) based communication link.
 40. A wireless terminal constrained tooperate within an aggregate transmit power limit, the wireless terminalincluding N wireless modems having their respective transmit outputscombined to produce an aggregate transmit output, comprising: means fordetermining an average energy-per-transmitted-bit across a plurality ofpreviously active ones of the N modems that were previouslytransmitting; means for determining, based on the averageenergy-per-transmitted-bit and the aggregate transmit power limit, amaximum number of active modems that can concurrently transmit data at amaximum data rate without exceeding the maximum aggregate transmit powerlimit; and means for scheduling data-to-be-transmitted over thedetermined maximum number of active modems.
 41. The wireless terminal ofclaim 40, further comprising: means for determining an aggregatetransmit power of the N modems corresponding to when the plurality ofactive modems were previously transmitting data; means for monitoringstatus reports from the N modems, the status reports indicating arespective transmit data rate for each of the N modems; and means fordetermining, based on the respective transmit data rates, an aggregatedata rate of the N modems corresponding to the aggregate transmit power,wherein the means for determining the maximum number comprises means fordetermining the average energy-per-transmitted-bit based on theaggregate transmit power and the aggregate data rate.
 42. The wirelessterminal of claim 40, wherein: each of the N modems is adapted totransmit data at at least one of a maximum transmit data rate and aminimum transmit data rate; and the means for determining the maximumnumber comprises determining the maximum number based on the minimum andmaximum transmit data rates as well as the averageenergy-per-transmitted-bit and the aggregate transmit power limit. 43.The wireless terminal of claim 40, wherein the means for determining theaverage energy-per-transmitted-bit, the means for determining themaximum number of active modems, and the means for scheduling repeattheir respective functions periodically, thereby causing the maximumnumber of active modems to vary over time in correspondence with theaverage energy-per-transmitted bit.
 44. A wireless terminal constrainedto operate within an aggregate transmit power limit, the wirelessterminal including N wireless modems having their respective transmitoutputs combined to produce an aggregate transmit output, comprising:means for determining an individual energy-per-transmitted-bit for eachof the N modems that was previously transmitting; means for determining,based on all of the individual energy-per-transmitted-bits and theaggregate transmit power limit, a maximum number of active modems thatcan concurrently transmit data at a maximum data rate without exceedingthe aggregate transmit power limit; and means for scheduling the maximumnumber of active modems to transmit data.
 45. The wireless terminal ofclaim 44, further comprising: means for sorting the N modems accordingto their respective individual energy-per-transmitted-bits, the meansfor scheduling comprises means for scheduling the maximum number ofactive modems having the lowest individual energy-per-transmitted-bitsamong the N modems.
 46. The wireless terminal of claim 44, furthercomprising means for monitoring status reports from at least the activemodems, the status reports collectively including a transmit powerestimate of each active modem, wherein the means for determining theindividual energy-per-transmitted-bits comprises means for determining,from each transmit power estimate, the corresponding individualenergy-per-transmitted-bit.
 47. An apparatus for dynamically calibratinga wireless terminal, the wireless terminal including N wireless modemshaving their respective transmit outputs combined to produce anaggregate transmit output, comprising: means for scheduling each of theN modems to concurrently transmit respective data, thereby causing eachof the N modems to concurrently transmit; means for receiving respectivereported transmit powers P_(Rep)(i) from the N modems corresponding towhen the N modems concurrently transmit, where i designates a respectivemodem from 1 to N; a power meter, coupled to the aggregate transmitoutput, for measuring an aggregate transmit power P_(Agg) of the Nmodems corresponding to when the N modems concurrently transmit; meansfor generating an equation representing the aggregate transmit power asa cumulative function of each reported transmit power P_(Rep)(i) and acorresponding, undetermined, modem dependent gain factor g(i), whereinthe scheduling means, the receiving means, the power meter, and thegenerating means repeat their respective functions N times to generate Nsimultaneous equations; and means for determining all of the modemdependent gain factors from the N simultaneous equations.